Janine Butler, a 28-year-old New Jersey teacher, knows something about out-of-control students.
One girl threw objects, threatened Butler with knives and tried to bite her. Another boy was "just rude, rude, rude," pulling down his pants and swearing at her. The final straw came when another student scratched and hit her.
Butler's students were barely out of diapers — 3- and 4-year-olds — and their public preschool in Trenton was not allowed to expel them.
"No one would do anything," said Butler, who eventually quit. "I felt alone."
Tantrums, aggression, biting and kicking are becoming increasingly common in preschool, according to child development specialists.
With bad behavior on the rise, so are preschool expulsions, according to a Yale University study published earlier this month.
Author Walter Gilliam, director of the Zigler Center in Child Development and Social Policy, told ABCNEWS.com that he didn't set out to study preschool expulsions. But when he was analyzing publicly funded prekindergarten policies at 3,898 schools in 40 states, he found expulsion rates three times higher than for older grades.
"Many teachers have anecdotally reported a perception of an increase in the rates over the past several years, but there are currently no scientifically collected data to confirm or deny this perception," he said.
Gilliam reported 6.7 expulsions per 1,000 preschoolers in the United States, compared with 2.09 per 1,000 for students in kindergarten through grade 12. In data collected from 2002-2004, rates ranged from zero per 1,000 students in Kentucky to more than 21 in New Mexico.
Private school expulsion rates were higher than for public school, and boys were four times as likely to be kicked out than girls.
Researchers identified a wide range of anti-social behavior — from cutting computer cords as a way to "liberate the mice" to hair-pulling. Biting was the most common offense.
"Nobody knows why," Gilliam said. "A lot of people blame parents. A lot of people blame the schools or an education system that pushed programs to preschool that are not developmentally appropriate. Now the stakes are higher in preschool."
Most public preschools must now submit accountability reports, according to Gilliam. "If behavior is a problem, in the past it was a nuisance, now it stands in the way of progress."
He concludes that expulsions set children up for educational failure and recommends better teacher training, smaller classes and greater classroom support from psychologists and social workers.
"We agree with the findings," said Don Owens, spokesman for the National Association for the Education of Young Children, who said many parents were afraid to talk openly with the media about their children's expulsions for fear of branding them.
"Expulsion should be the last resort, but unfortunately, it has become the first resort," he said.
Some studies show that aggression in preschool may be an indicator of delinquency and crime later on, according to a policy report by the National Institute for Early Education Research, which helped fund the Yale study.
NIEER's review of national research suggests bad behavior may be up for a variety of reasons: poor prenatal care, including drug use; family poverty and "negative parenting practices, such as harsh discipline and maternal insensitivity."
The school environment for these early learners may be to blame.
But NIEER cautions that some of these behaviors are normal at this age.
"Hitting your sister is not aggression," said NIEER co-director Ellen C. Frede. "It's the 'super nanny' stuff that you see. Kids doing things over and over like eating dog food and biting mom and destroying things and being incredibly defiant and outside the pale."
Many teachers, like Butler, worry that some children lack the social skills required to learn.
"The teacher needs support — not always a mental health consultant but good old-fashioned behavior management," said Frede. Some children need a "well-organized curriculum" and others just lack parents who are engaged in their lives.
"Just as parents come in different flavors, so do teachers," said Frede. "Sometimes there is too much structure and the child cannot handle it. Other times, the teacher doesn't have enough organization and loses the confidence and trust of her children, who then act out. Three years old is a challenging period."
Poverty and overcrowded classes exacerbate the behavior problems. "My parents cared more about buying their kids new Nikes than giving them a Kleenex when they had a cold," said Butler, who is now teaching in a another preschool.
Colorado mother Amy Gates, who blogs about parenting on crunchydomesticgoddess.com, said preschool expulsions are "kind of shocking." Her 3-year-old attends a private preschool and has had brushes with bad behavior.
When her daughter pushed another child to grab a toy, the teacher used "gentle discipline" to curb any budding aggression.
"There is going to be some acting out in the classroom, especially with preschoolers because they are just learning their boundaries and learning what's acceptable or not," she said.
Andi Silverman, author of "Mama Knows Breast" and contributor to the New York City Moms Blog, said she worries more about accidents in her 3-year-old son's classroom than aggression.
"Expelling a child from preschool is a very harsh measure," she said. "Hopefully, parents and teacher work together."
In New York City, where getting into exclusive preschools is as hard as getting a fat acceptance letter from Harvard, parents and children are screened carefully before they are admitted, according to Silverman.
Most of the nation's preschools are run privately and are not obligated to serve a difficult child, said Karen Hill Scott, a Los Angeles development psychologist and researcher.
"If the child is a problem, they don't have to support them," said Scott. "Public schools have to figure out a way to manage them."
The rise in socially aggressive children is a "warning sign" that reflects directly on parenting, according to Scott.
"There is an inadequate emphasis on self-regulation and self-control," according to Scott, who said adults with low impulse control are less successful in work and in human relations.
Parents confuse "indulgence with love," said Scott. "The helicopter parent hovers, and kids don't learn to fend on their own. The indulged kids never delay any gratification. When everything goes your way, you have a hard time working in groups."
With more children in preschool, the behaviors that once played out in first grade now emerge "in the toddler room," she said.
Aviva Pflock, a former preschool teacher and child development specialist, said, "The fact is, 3, 4, 5, 6, even 7, and older age children simply are not ready to make choices in regards to how their behavior affects others. They get angry [or tired or hungry], and they may lash out. Rather than getting in trouble for the poor behavior, they need to be taught about appropriate ways to behave."
But, argues NIEER's Frede, most children only need a good quality program and a teacher who is well-trained and well-compensated. And maybe some old-fashioned discipline.
When Frede's mother was a preschool teacher in the late 1950s and had a biter in her class, she whisked the child away into a closet and asked him to "bite himself," to see how it felt.
Not that Frede recommends that unorthodox method today, but she said with a laugh, "Joel never bit another kid."